Windows Network Address Translation (NAT) Spoofing Vulnerability

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-56181
StatePUBLISHED
Assignermicrosoft
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-14 18:18:24 UTC
Updated2026-07-22 16:18:26 UTC
DescriptionOrigin validation error in Windows Network Address Translation (NAT) allows an unauthorized attacker to perform spoofing over an adjacent network.

Risk And Classification

Primary CVSS: v3.1 8.3 HIGH from [email protected]

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS: 0.002420000 probability, percentile 0.154900000 (date 2026-07-22)

Problem Types: CWE-346 | CWE-346 CWE-346: Origin Validation Error

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.3HIGHCVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
3.1CNACVSS8.3HIGHCVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Microsoft Windows 11 24h2 All All All All
Operating System Microsoft Windows 11 25h2 All All All All
Operating System Microsoft Windows 11 26h1 All All All All
Operating System Microsoft Windows Server 2025 All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Microsoft Windows 11 Version 24H2 affected 10.0.26100.0 10.0.26100.8875 custom ARM64-based Systems, x64-based Systems
CNA Microsoft Windows 11 Version 25H2 affected 10.0.26200.0 10.0.26200.8875 custom ARM64-based Systems, x64-based Systems
CNA Microsoft Windows 11 Version 26H1 affected 10.0.28000.0 10.0.28000.2525 custom ARM64-based Systems, x64-based Systems
CNA Microsoft Windows Server 2025 affected 10.0.26100.0 10.0.26100.33158 custom x64-based Systems
CNA Microsoft Windows Server 2025 Server Core Installation affected 10.0.26100.0 10.0.26100.33158 custom x64-based Systems

References

ReferenceSourceLinkTags
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56181 [email protected] msrc.microsoft.com Patch, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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